1. Field of Invention
This invention relates to backpacks, particularly to simple, inexpensive single-compartment backpacks.
2. Prior Art
A typical low-cost, one-compartment backpack is a sewn cloth bag with a drawcord closure. The two strands of the drawcord that emerge from the closure sleeve on top are attached, usually by knots and grommets, to the lower corners of the bag, thus forming shoulder loops. Cord length is adjusted by retying the knot elsewhere on the cord.
Painful cords.
As the load increases in weight, these cords become painful on the wearer's shoulders. Although some bags of this kind use flat webbing straps to avoid this problem, friction makes them clumsy to open and close, and no strap adjustability is provided, since straps make extremely unsatisfactory knots. They are simply sewn into the hem.
A waist cord attempt.
Although most drawcord type backpacks do not provide a waist cord, U.S. Pat. No. 4,674,664 to J. D. Simon (June 1987) shows a way to do this. However, not only does this bag need the usual reinforcing, grommeting, and sewing to assemble, but in addition, four separate cords need to be tied together in a complex configuration, two of them threaded through the closure sleeve in opposite directions. Clearly, this much hand assembly is expensive. Moreover, this bag does not solve the problem of painful cords since its intended use is carrying only the few lightweight personal effects needed by runners, bicycle riders, skiers, etc. Neither is there any interest in, nor attempt to provide a display area, or foul weather protection. On the contrary, the preferred embodiment calls for an open mesh material.
The "bunching-up" factor.
Whatever the materials used, all drawcord bags have a serious built-in contradiction; their tops bunch up into an ugly knob when drawn closed, and the heavier the material used, the bigger the bunch, and the less adequate is the closure, because of the center hole it forms, which can never be closed completely. The use of flat straps only exacerbates this problem.
Furthermore, the bunching obscures any graphics that might be imprinted on the upper portion of the bags, limiting its useful display area to the lower portion.
These drawcord-type bags often have a weather flap sewn on the back to cover the center hole that remains after closure. The loose end of this weather flap is attached to the front of the bag with one or two buckles, all of which puts the bag into a higher price category. This flap usually covers the drawcord in use, which therefore cannot be used as shoulder straps, so another set of straps must be sewn on for that purpose, adding to the complexity--and cost.
A single strap attempt
Attempts have been made to use a single strap for both closure and shoulder use. (German patent 693,272 to E. Weber (July 1940) shows such a single strap, but to work properly, the strap has to remain so narrow that it provides hardly any advantage over a cord for pain-free portaging. Besides, the bag clearly requires expensive hand construction by sewing, grommeting, etc., as does every other conventional backpack.
The limitations of sewing.
All other factors being equal, backpacks that must be entirely sewn together cannot be made as cheaply in large quantities as ones that can be produced without the need for any sewing whatsoever--especially with high speed automatic equipment performing most of the task.
Furthermore, sewing is actually destructive, since it repeatedly penetrates the bag material, thereby weakening it. That is one reason why most available low-cost backpacks don't last. They are not reinforced at stress points, since this would raise the price.
The peel-stress factor.
U.S. Pat. No. 4,273,274 to M. S. Freistadt (June 1981) shows a handbag that is convertible to a backpack. Its convertibility notwithstanding, this bag fails as a backpack for these reasons:
First, this entirely sewn--therefore comparatively expensive--bag shares the major pitfall of all sewn backpacks that rely solely on strap fastening points that originate on the same side of the bag that the bearer occupies; these sewn connections must alone withstand the enormous peel forces this type of design generates. In use, the bag is pulled in one direction, the straps in another, and only the first stitch in a row of stitches holds them together. Unless heavily reinforced at additional cost, that first stitch at the point of greatest stress fails, then the next, and the next, etc. Second, the crossed straps over the bag top may provide some measure of security for large objects contained in the bag, but very little for smaller ones, and none for any object that requires protection from foul weather.
Backpacks not used as promotion bags.
Inexpensive bags are widely used for promotion purposes, so their utility, relative low price, and ability to bear an image are important. The flexible woven fabrics used for drawcord bags have too coarse a surface for fine printing. Besides, these materials cannot be handled by standard high-efficiency printing presses, so graphics are limited to the relatively slow screen printing of flat, crude images, like logos. Better--but by no means fine--printing is being done on plastic bags of this type, which are heat-sealed together, but these tend to be too lightweight for even moderate and repeated portaging.
Whatever the graphics imprinted on them, since conventional tote bags are carried down, at or below knee height, any graphics they bear are poorly displayed well below eye level. On the other hand, any imprinted backpack, low-cost or otherwise--in theory--provides superior eye-level display. But, although widely available for this purpose through advertising specialty distributors, they are conspicuously unpopular as promotion bags because even the moderately good ones are too expensive, the images they can bear are too crude, and the display area is too small.
The lack of well-printed bags for children.
Many parents of early school-age children want their offspring to be comforted by an image of a beloved media character accompanying them when they go to school. Backpacks with cartoon characters on them are available, but their high prices, poor choice of characters, and poor quality keep them from being popular. One reason they are expensive is that the methods used to apply the images onto materials that are suitable for sewing are costly. Another reason is these bags tend to be bulky and occupy too much valuable store space. Store buyers tend to order them only for the "back-to-school" season, when interest is greatest. Even then, expecting sluggish sales, buyers are careful not to over-order, so choice of characters is limited. The images themselves tend to be small and unappealing because they must, of necessity, be confined to one or two panels of the several these sewn bags comprise.
Quality versus graphics.
As children grow through their school years, so does their need for sturdier, more durable backpacks. Given the limitations of sewing technology, this necessary added value inevitably leads to not only higher prices, but an abandonment of another value, visual appeal. Available backpacks are monochrome, and dull to look at. Images on them are relegated to small sewn-on embroidered patches, or at most, a change of fabric color from panel to panel in an attempt to brighten them. Some backpacks are made of embroidered, or otherwise patterned fabrics, but these sacrifice sturdiness, and cost no less. There have been no visually appealing backpacks that are also durable, and low cost.
Quality versus ease-of-use.
Certain large segments of the population, such as non-driving city dwellers, have a greater need to carry things unassisted, so the methods they use are significant. One such growing segment is the independent elderly, who have trouble dealing with their everyday carrying needs. Hands-free portaging is a necessity for them, since they need to hold on to supports in order to keep balance, push elevator buttons, handle keys, wallets, purses, cards, etc., so backpacks are potentially extremely useful to them. But, such older persons wearing backpacks are hardly ever seen. One reason for this is the available backpacks of even moderate capacity and reasonable quality are too expensive due to their complex, reinforced construction, and they weigh too much. Another reason is they are difficult for the elderly to use. Inexpensive backpacks are usually just a flat cloth sack without side walls, or a floor. Consequently, they have no structure that would enable them to stand up unsupported, so loading can be clumsy. After loading, the user has to first pull and tie the drawcord, buckle the flap, and then make twisting overhead, or behind-the-back moves to put the bag on, and then reverse these steps prior to unloading. All these efforts are hardly worthwhile for a short trip to the store for a few items, even for a young and agile person.